Ranger 1964-65

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8/7/2019 Ranger 1964-65


RANGER 1964-65

J E T P R O P U L S I O N L A B O R A T O R Y

C A L I F O R N I AN S T I T U T EF T E C H N O L O G Y

P A S A D E N A ,A L I O R N I A

July 1964

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The time has at last arrived when man stands ready to begin the long-awaited lunar

explorations.

In roduc ion

During the years 1964-65 a series of Ranger spacecraft

will be launched on a Moon-impact trajectory. This series

is identified as the Ranger Block I11 Project.

The mission of the Block I11 Ranger flights is to obtain

television pictures of the lunar surface and to develop

some of the required technologies, operational skills, and

procedures that will be necessary to the ApoZZo Project.

The Ranger missions utilize the General Dynamics/

Astronautics Atlas D, a modified Air Force missile, and

the Lockheed Agena B second-stage rocket. The Ranger

spacecraft, mounted atop the Atlas-Agena combination

launch vehicle, carries a multiple TV camera subsystem

built by Radio Corporation of America (RCA). A series

of up to about 4200 video pictures, commencing approxi-

mately 14 minutes before lunar impact, is expected to be

obtained by each mission. However, because the cameras

are set to a wide range of lighting conditions, it is not

expected that all pictures will record useful information.

The pictures expected should be at least an order of

magnitude better in resolution than any Earth-based

photography.

Success of the Ranger mission is dependent upon the

proper functioning of the four major systems:

(1 )The Launch Vehicle System which must place the

spacecraft into its proper orbit.

(2 )The Spacecraft System which must perform all of

its programmed activities successfully and at the

proper time.

(3 )The Deep Space Instrumentation Facility which

tracks the spacecraft, transmits the necessary com-

mands to it, and receives its transmitted information.

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(4) The Space Flight Operations System which has

direct control of the spacecraft during the phases

of its flight and from where the commands are

generated, information gathered and stored, and

trajectories plotted.

These four systems are integrated under the over-all

management of the Jet Propulsion Laboratory, California

Institute of Technology, Pasadena, as directed by the

Office of Space Science of NASA. The Lewis Research

Center, an agency of NASA, is responsible for the Launch

Vehicle System. The three remaining systems of the

Ranger Project are under JPL management.

In the case of a nominal trajectory, approximately

67 hours after launch, the spacecraft will be about 3940

miles from the Moon and falling toward it at a velocity of

about 3400 miles per hour. At 14 minutes before impact,

the TV subsystem is programmed to begin viewing the

lunar surface, translating the lunar scene into video data

for transmission back to Earth. During this 14-minute

period, the Ranger completes its photographic mission,

impacts the Moon, and is destroyed.

Notwithstanding the severe weight and space limi-

tations that restrict the amount of spacecraft video equip-

ment to less than 400 pounds compressed within a few

cubic feet, the highly developed RCA TV subsystem is

capable of producing high-resolution TV photographs of

the Moon. These video pictures will be transmitted a

distance of 2000 times greater than the maximum range

of commercial TV stations operating under the most

favorable conditions. This photographic data, transmitted

back to Earth by spacecraft, will help to fill the urgent

need for lunar surface data required for NASA's soft

landing instrumented spacecraft Surveyor, and for the

Apollo mission.

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A closeup look at the lun ar surface is necessary in order to prepare for future in -

strumented soft landings and finally the manned missions.

Our Satellite, The Moon

The Moon, our closest celestial neighbor and the object

of legends and superstitions since history began, is as

familiar to us as is the face of a close friend. We know

the solemn beauty of the full Moon and the half comic,

half frightening face of the “Man in the Moon.” Poets

ponder the influence of the ever-constant Moon on

romance. Children speculate whether or not it is really

made of green cheese. And more sober adults smile con-

descendingly a t both of these theories. Yet very lit tle is

actually known about the Moon.

A prehistoric remnant, relatively unchanged for billions

of years, the Moon may prove to be the Rosetta Stone

that will unlock many of the secrets of t he origin and

evolution of our solar system.

In 1609 Galileo described his observations of the Moon

as follows:

are seen to be drawn out in long tracts of hundreds of

miles. Others are in more compact groups, and there are

also many detached and solitary rocks, precipitous and

craggy. But what occur most frequently there are certain

ridges, somewhat raised, which surround and enclose

plains of different sizes and various shapes but for the

most part, circular. In the middle of many of these there

is a mountain in sharp relief and some few are filled with

a dark substance similar to that of the large spots that

are seen with the naked eye; these are the largest ones,

and there are a very great number of smaller ones, almostall of them circular.” a

Galileo first gazed at the Moon through a telescope

more than 350 years ago. Since that time, however, we

have seen little more of the detail of the Moon’s surface

than did Galileo. Our modern telescopes are better, but

we still stand the same distance from the Moon and on

“The prominences there are mainly very similar to our

most rugged and steepest mountains, and some of them

a“Ga1ilei Galileo”; p. 63; dialogue concerning the two chief world systemsPtolemajc and Copernican; Translation by Stillman Drake; Foreword b;Albert Einstein; University of California Press, Berkeley, California.

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Photo courtesy Mt. Palomar Observatory

Figure 1. Crater Clavius an d surrounding regions

Photo courtery l ick Obrervatory

the same platform-the Earth. We still must peer through

the same mantle of atmosphere that hindered Galileo’s

viewing. That blanket of life-giving air that protects

Earth life and causes the stars to twinkle so delightfully

unfortunately makes the details of the Moon twinkle also.

Although the lunar surface conditions still elude us, we

have learned a few facts about the Moon. We concludethat the Moon has no surface water and no appreciable

atmosphere. For all practical purposes, its distance from

the Sun is the same as the Earth’s, and so it receives the

same amount of heat from the Sun. But, due to the lack

of atmosphere, the temperature on the Moon’s surface

ranges from 261°F at noon, hotter than boiling water on

Earth, to -243°F at midnight-more than twice as cold

as any place on Earth. Such extremes of temperature,

coupled with the lack of atmosphere on the Moon, would

presumably preclude the existence of any form of life as

we know it. Still the possibility of the existence of so-

called sub-life forms must be considered. The action ofatoms and molecules at the surface, or just under the

surface of the Moon, under eon-long bombardment by

undiluted solar radiation and by cosmic rays, cannot be

predicted. The formation of complex macro-molecules

may be possible.

Additionally, the Moon has a diameter of about 2163

miles-about one-quarter that of Earth. Because it is

smaller than Earth, its gravity is much less. Standing on

the surface of the Moon, one would weigh only one-sixth

as much as he weighs on Earth. The density of the Moon

is 3.3 times that of water, while that of Earth is 5.5.Scientists agree that the Moon’s mass is about 1%percent

of the Earths mass. The lunar world is in a slightly ellip-

tical orbit at an average distance of approximately 238,000

miles from Earth. The Moon requires 27% days to make

a complete orbit of Earth and, because its rotational

period is the same, it always presents the same face

toward Earth.

The Moon generates no light of its own and shines

solely by reflected Sunlight or Earthlight; only 59% of

its surface is visible from Earth. The Moon has no obvi-

ous effect on the climate of the Earth, but is the dominant

factor in the production of tides. There is also some slight

but distinct relationship between the changes of distance

of the Moon from the Earth and variations in terrestrial

magnetism.

Figure 2. lunar region of craters Copernicus

and Eratosthanes

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.-

Photo rourt*ry l ick Obs*natory

Figure 3. lun ar area, southwestern margin

of Mare lmbrium

Recent studies have made it appear probable that the

great craters on the Moon are impact craters rather than

volcanic craters (Figs. 1 and 2). It also seems that at least

some of the maria (the great plains) are the direct result

of impact (Fig. 3). It is not clear if the impacts

acted primarily as a trigger mechanism releasing molten

material (if any) from the Moon’s interior, or if themelting material resulted primarily from the kinetic

energy of the impacts.

Although the great craters appear to be meteoric in

origin, this does not imply that no volcanic activity can

exist on the Moon. On the contrary, there are rows of

craterlets, near Copernicus, which may be due to volcanic

activity. One of the most interesting observations in the

past few years was made in a portion of the crater

Alphonsus. A temporary haziness was found which lasted

long enough to obtain a spectrogram confirming th e

existence of carbonaceous molecules and some yet un-

identified species. So gases do exist, at least for a short

time, on the surface of the Moon. This “atmosphere” is

very tenuous at best and must consist primarily of a few

stray molecules of heavy inert gases. Perhaps a few light

gases are in existence for a short time and immediately

after a volcanic emission. Additionally, in recent months,

unidentified temporary reddish areas have been sighted

in other parts of the lunar surface.

One school of thought suggests that the maria, or

plains, as well as the centers of many of the old craters,

are filled with dust. The thickness of the layer of dust is

estimated by the total amount of rock which could have

been worn from all of the old crater walls in the high-

lands. On this basis, a number of 1 kilometer is reached

for the maximum dust depth-that is, a little over M mile.

Experiments have indicated that dust, in a vacuum

such as on the surface of the Moon, would tend to

become hard packed. So we can imagine that any deep

dust layer on the Moon would resemble pumice more

than the dust with which we are familiar. Accordingly,

there would seem to be little danger of our spacecraft

being buried in a half-mile of loose dust. However, there

are also the theories of suspended dust, sintered dust,

and no dust at all. Thus, the most important task we

must accomplish in the early stages of lunar exploration

will be to determine the exact nature of the Moon’s sur-

face. This will be the starting place, and eventually all

the questions will be answered. The exact nature of the

Moon’s surface is extremely important to the basic designof both unmanned and manned lunar spacecraft; unfor-

tunately, it is not possible to resolve these questions

by looking through our telescopes.

In the photograph (Fig. 4) the Mare Imbrium-the

right eye of the man in the Moon-is seen (top left). This

is one of the level plains or maria. Standing out on the

plain just below the outer rim of mountains is Mt. Piton.

In the photograph (taken by Lick Observatory, Univer-

sity of California, Mt. Hamitton, California), Mt. Piton

appears as a small, jagged hound’s tooth, I t is possible to

measure heights on the Moon with surprising accuracyby measuring shadow lengths. A better understanding of

the actual configuration of Mt. Piton may be obtained by

considering ourselves as Moon explorers, standing on the

surface of the Moon, a few miles from its base. From

here it would appear as a high but gentle sloping moun-

tain rising to about 7000 feet and stretching out more

than 70,000 feet (about 13 miles). The top is so nearly

level that it would be difficult to determine the highest

point. Certainly, from this point of view, it looks very

different from the rugged mountain it appears to be in

the photograph.

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In pictures of the Moon taken with the 2OO-inch tele-

scope at Palomar at high magnification (Fig. I), the small-

est detail that can be seen is almost a mile across. Details

smaller than that are simply unresolved and must await

the actual landing of our scientific instruments on the

Moon or close distance photographing of the Moon bycameras operating outside the distortion of the Earths

atmosphere.

Pholo courtesy Lick Observatory

Figure 4. Eastern part of the Moon

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The launching problem i s severe: The Moon is a most difficult ta rget and the launch

constraints are many.

The Launch Problem

The launch problem is partially illustrated in Fig. 5 .

It is helpful to envision the path of the spacecraft as a

tunnel through which the spacecraft passes on the way

to its destination. The entrance to this tunnel is actually

the injection point of the spacecraft, the point at which

the Agena booster ceases to impart velocity to the space-

craft. The entrance to this tunnel begins at a point

approximately 115 miles above the Earth, is about

10 miles in diameter, and extends to the Moon. Because

of the curved nature of the trajectory, the distance the

spacecraft must travel is about ?hmillion miles, although

the average, straight-line distance to the Moon at thelaunching time is approximately 238,000 miles.

Some of the factors, imposed by the nature of the solar

system, that complicate the role of the launch vehicle are:

(1)The Earth is rotating on its axis, making one com-

plete turn every 24 hours. The launch site, being

located in Florida approximately 30 degrees north

of the Equator, therefore turns through space at

a speed of nearly 1000miles per hour.

(2)The target, the Moon, is orbiting the Ear th at a rate

(3)For technical reasons, the time of arrival of the

spacecraft at the target must occur during the

Goldstone Tracking Station view period. The time

of arrival is also critically related to the illumination

conditions of the lunar surface, and hence to the

success of the picture-taking mission.

the Earth‘s mantle of atmosphere.

of approximately 2000 miles per hour.

(4)Escape velocity can only be reached safely outside

Additional constraints also arise from the fact that the

launch vehicle’s path over the Earth must be restricted

to a corridor that would preclude any portions of the

A t b A g e n u launch vehicle from impacting any popu-

lated areas or endangering shipping lanes. In view of

these factors, the exacting role of the launch vehicle

becomes more apparent.

The launch corridor is shown in Fig. 6. It extends

normally from a launch azimuth of 90 to 114 degrees in a

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EARLY IN DAY h, M O O N.NORTH POLE

ATFIR

1s t AGENAFIRING

LATER IN DAY

AGENA COASTSIN CIRCULARPARKING ORBITAT 17,500 MPH,ALTITUDE 1 15 MI.

RELATIVELY FIXEDIN SPACE F O R AN YONE LAUNCH DAY

IF RANGER ENTERS 10-MILE-DIAMETERCIRCLE WITHIN 16 MPH OF DESIREDINJECTION VELOCITY, THEN MIDCOURSEMOTOR CAN ADJUST TRAJECTORY FOR

LUNAR IMPACT. DESIRED INJECTIONVELOCITY VARIES FROM 24,463 TO 24,487MPH DEPENDING ON DATE OF LAUNCH

AGENA COASTTIME SHORTER

Figure 5. Typical Ranger launch to Moon

southeasterly direction from Cape Kennedy in Florida.

The exact trajectory chosen for any particular flight

depends upon the day of the month and the time of day

of the launch. Therefore, as seen from the Earth, the

exact location of the injection point varies as a function

of launch date. Additional factors, caused by the missionobjectives and the technical requirements of the space-

craft and its Earth-based support equipment, place even

further restraints on the launch. All these and other perti-

nent factors are taken into consideration in the design

and selection of the trajectory to be flown by the launch

vehicle and spacecraft.

For the few consecutive days that occur during each

month when the geometric relationship of the Earth,

Moon, and Sun would permit a successful launch (Fig. 7),extensively detailed tabulations of the velocity, position,

and acceleration necessary to put the spacecraft into orbit

are computed for each day and recorded. These tabula-tions become the standards from which flight paths for

virtually any moment of the day can be projected. The

primary variables used to compensate for the changing

celestial geometry are the launch azimuth and the length

of time the vehicle is allowed to remain in the parking

orbit. The parking orbit is an advanced technique requir-

ing the use of a second-stage vehicle equipped with a

restartable rocket engine. At the conclusion of the first

burn of the Agenu B engine, the second stage has at-

tained sufficient velocity to orbit the Earth as a near-

Earth satellite at an altitude of about 115 miles. The

vehicle then coasts to a proper location over the mid-

Atlantic where the rocket engine is restarted to accelerate

the spacecraft to escape velocity. Accordingly, the exactazimuth of the actual launch dictates the specific set of

trajectory computations used as the standard by which

the normalcy of the flight is judged.

Stated in its most fundamental form, the space mission

is composed of these tasks:

(1) Placing a spacecraft into a path or trajectory that

will carry it to its desired destination.

(2) Tracking the spacecraft during its flight for its

actual position, velocity, and direction of travel so

that proper corrections to its trajectory may be

made if required.

(3) Maintaining continuous two-way communications

with the spacecraft in order to command operational

changes if required, and receiving on the ground

the data it is producing.

(4) xecuting the engineering and scientific tasks

through the use of instruments aboard the space-

craft.

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Figure 7. Trajectory limitations on Ranger Block 111 missions

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Close determination of surface characteristics o f the Moon i s required for future

instrumented soft landings and finally manned missions.

Spacecraft

Description

The Ranger spacecraft (Fig. 8) is a basic unit capable

of carrying as its passengers various types and kinds of

instruments. This unit (or bus) provides power, commun-

ication, attitude control, command functions, trajectory

correction, and a stabilized platform upon which the

scientific instruments can be mounted. The spacecraft is

designed to accomplish certain tasks during predeter-

mined periods of the flight. These periods are:

(1)The liftoff-to-injection period, or launch mode.

The basic spaceframe is composed of a series of con-

centric hexagons constructed of aluminum and magne-

sium tubing and structural members. Electronic cases are

attached to the six sides and a high-gain, dish-shaped

antenna is hinged to the bottom. Sun sensors and attitude

control jets are mounted on four of the legs of the hexa-

gon. The midcourse motor is set inside the hexagonal

structure with the rocket nozzle facing downward. The

bus also includes a hat-shaped omnidirectional antenna

which is mounted at the peak of the conical structure.

(2) Earth and Sun acquisition m=ineuverS that Place

the 'pacecraft in cruise mode, for the perid Of

normal flight.

~~0 solar panels (Fig. 9) are hinged to the base of the

hexagon and are folded alongside the spacecraft during

launch. During the period of flight, the panels are un-

folded horizontally when the spacecraft is in its space

attitude. The panels provide 24.4 square feet of solar cell(3 ) The midcourse maneuver to correct the flight tra-

jectory if necessary.area which, when exposed to Sun, will deliver 200 watts

of raw power to the spacecraft. There are 4896 solar

cells in each panel.

(4) The terminal maneuver which orients the space-

craft to meet the requirements of the instruments.

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Table 1. Ranger space vehicle

Launch vehicle ................................. Atlas-Agena B

Dimensions (launch vehicle)

Total height, with Ranger spacecraft, plus shroud. . . 100 plus feet

Atlas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66feetAgena B ........................................... 12feet

Dimensions (Ranger)

In launch position, folded

Diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 feet

Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.25feet

In cruise position, panels unfolded

Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15feet

Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.25feet

Approximate weigh t (Ranger)

Structure .................................... 90 pounds

Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 pounds

Propulsion .................................. 45 pounds

Launch back-up battery ...................... 51 pounds

Miscellaneous equipment . . . . . . . . . . . . . . . . . . . . . . 37 pounds

TV subsystem total .......................... .382 pounds

Solar panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 pounds

Ranger bus total . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 pounds

Gross weight of the spacecraft . . . . . . . . . . . . . . . . . . 806 pounds

and transmitter; case 3, data encoder (telemetry); case 4,

attitude control, (command switching and logic, gyros,

autopilot); case 5, spacecraft launch and maneuver bat-

tery; case 6A, power booster regulator, power switching

logic, and squib firing assembly; case 6R, second space-

craft launch and maneuver battery.

Two antennas are employed on the spacecraft. The

low-gain, omnidirectional antenna transmits during the

launch sequence and the midcourse maneuver only. It

functions at all other times throughout the flight as a

receiving antenna for commands radioed from Earth.

A dish-shaped, high-gain directional antenna (Fig. 11)

is employed in the cruise and terminal modes. The

hinged, directional antenna is equipped with a drive

mechanism allowing it to be set at appropriate angles.

An Earth sensor is mounted on the antenna yoke near

the rim of the dish-shaped antenna to search for, and

keep the antenna pointed at, Earth. During midcourse

maneuver, the directional antenna is moved out of the

path of the rocket exhaust, and transmission is switched

to the omni-antenna.

The midcourse rocket motor (Fig. 12) is a liquid mono-

propellant engine weighing, with fuel and nitrogen

Figure 9. Ranger solar panel

showing hinge actuator

a

@iD-

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pressure gas system, 46 pounds. Hydrazine fuel is held

in a rubber bladder contained inside a doorknob-shaped

container called the pressure dome. On the command to

fire, nitrogen, under 300 pounds of pressure per square

inch, is admitted inside the pressure dome and squeezes

the rubber bladder containing the fuel.

The hydrazine is thus forced into the combustionchamber. A small quantity of oxidizer is used to initiate

combustion, and a catalyst to maintain combustion. The

starting fluid used, in this case nitrogen tetroxide, is ad-

mitted into the combustion chamber by means of a

pressurized cartridge. The introduction of the nitrogen

tetroxide causes ignition, and the burning in the com-

bustion chamber is maintained by the catalyst-alumi-

num oxide pellets stored in the chamber. Burning stops

when the valves turn off nitrogen pressure and fuel flow.

At the bottom of the nozzle of the midcourse motor

are four jet vanes which protrude into the rocket exhaust

for attitude control of the spacecraft during the mid-

course motor burn. The vanes are controlled by an auto-

pilot linked to gyros.

The midcourse motor is capable of firing in bursts as

short as 50 milliseconds, and can alter velocity in any

direction by as little as 4 nches per second or as much

as 190 feet per second. It has a thrust of 50 pounds for

a burning time of more than 90 seconds.

ELECTRONIC

ASSEMBLY

Plan view from top showing six magnesium

chossis hinged in op en po sition

ELECTRONIC

POWER

ASSEMBLY-VI-A

ELECTRONIC

ASSEMBLY-IV

ATTITUDE

CONTROL

ELECTRONIC

ASSEMBLY-ICC&S

AND COMMAND

ELECTRONIC

ASSEMBLY -I ASSEMBLY-Ill

COMMUNICATIONSENCODER

Figure 10. Subsystem cases on spacecraft-

hexagonal structure

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Figure 1 1 . High-gain directional antenna

Aboard the spacecraft are three radios: the 3-watt

receiver-transmitter in the bus and two 60-watt trans-

mitters. These transmit, during terminal maneuver, the

images recorded by the six television cameras. One trans-

mitter handles the two full-scan (wide-angle) cameras;the second transmits data from the four partial-scan

(narrow-angle) cameras.

During the cruise portion of the flight, before the

cameras are switched on for the terminal maneuver, the

bus transmitter transmits telemetry, (engineering data)

for both bus and TV subsystem.

A total of 110 engineering measurements (tempera-

tures, voltages, pressures) of the spacecraft are telern-

etered back to Earth during the cruise portion of the idccurse racket motor

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flight. This includes 15 data points on the television

subsystem. During terminal maneuver, with the television

turned on, the radios transmit additional engineering

data on the TV subsystem mixed with signals represent-

ing the television images. During the terminal maneuver,

90 additional engineering measurements on the space-

craft are transmitted.

The communications system for the bus includes data

encoders that translate the engineering measurements

into analog values for transmission to Earth; and a detec-

tor and a decoder, in the command subsystem, that trans-

late incoming commands to the spacecraft from a binary

form into electrical impulses. Commands radioed to the

spacecraft are routed to the proper destination by the

command subsystem. A real-time command, (RTC) from

Earth actuates the designated relay within the command

decoder, thus executing the command. Stored commands

are relayed to the CC&S in serial binary form to be held

and acted upon at a later time.

The television subsystem includes separate encoders

to condition the television images for transmission in

analog form.

Stabilization and maneuvering of the spacecraft in

pitch, yaw, and roll (Fig. 13) are provided by 12 cold

gas jets mounted in six locations and fed by two titanium

bottles containing a total of 5 pounds of nitrogen gas

pressurized at 3500 pounds per square inch. The jets are

linked by logic circuitry to three gyros in the attitude

control subsystem, to the Earth sensor on the directionalantenna, and to six Sun sensors mounted on the space-

craft frame and on the backs of the two solar panels.

There are two complete gas jet systems of six jets and

one bottle each. Either system can handle the mission

requirements in the event the other system fails.

The four primary Sun sensors (Fig. 14) are mounted

on four of the six legs of the hexagon; the two secondary

sensors are mounted on the backs of the solar panels.

These are light-sensitive diodes which inform the attitude

control system when they see the Sun. The attitude con-

trol system responds to these signals by turning the

spacecraft and pointing the longitudinal or roll axis

toward the Sun. Torqueing of the spacecraft for these

maneuvers is provided by the cold gas jets fed by the

nitrogen gas regulated to 15 pounds per square inch

pressure.

Computation and the issuance of commands are the

functions of the digital CC&S. All in-flight events per-

formed by the spacecraft are contained in three CC&S

sequences. The launch sequence controls events from

Figure 14. Sun sensor

launch through the cruise mode. The midcourse propul-

sion sequence controls the mid.eourse trajectory correc-

tion maneuver. The terminal sequence provides required

commands as Ranger nears the Moon.

The CC&S provides the basic timing for the spacecraft

subsystems. This time base is supplied by a crystal con-

trolled oscillator in the CC&S operating a t 307.2 kilo-

cycles. This is divided down to 38.4 kilocycles for timing

in the power subsystem, and divided down again for

use by other subsystems to 2.4 kilocycles, 400 cycles,

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P

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W I D E - A N G L E C A M E R A S

Figure 15. Ranger fv subsystem

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and 25 pulses per second. The control oscillator provides

the basic counting rate for the CC&S to determine issu-

ance of commands at the right time.

The six TV cameras (Fig. 15) are housed in a riveted

aluminum structure with a removable conical cover. The

cover is a load-bearing part of the structure and provides

a thermal control function. Fins are attached to the cover

to intercept the Sun’s rays in order to provide adequate

heat during cruise. The entire cover radiates heat during

the 14 minutes of the terminal phase when the television

subsystem is operating at full power.

Instructions radioed to the spacecraft for the terminal

maneuver are computed to orient the spacecraft to

point the cameras downward as Ranger drops toward

the Moon’s surface. The cameras’ line of sight is nom-

inally down the descent path. To achieve this, the

spacecraft will descend to the Moon’s surface tilted at an

angle of 38 degrees relative to the descent path.

Since the exact light level on the Moon is unknown,

certain lighting condition assumptions, based on the best

available information, must be made. The cameras are

adjusted to cover as broad a range of^lighting conditions

as is feasible. A successful photographic mission will

provide more exact data on lunar lighting for finer

camera adjustment for use on later missions.

The 382-pound television system was designed for the

Ranger by RCA’s Astro-Electronics Division, Princeton,

New Jersey.

As Ranger approaches the Moon, it will take about

4200 television pictures of a selected portion of the sur-

face before it crashes at 6000 miles per hour. The first of

these pictures, to be taken at a distance of about 1120

miles from the Moon, will be roughly comparable in

resolution to those taken by large telescopes on Earth.

As the spacecraft descends upon the Moon, the pictures

improve in quality and resolution. The last few pictures

taken, those taken just before the Ranger crashes, may

distinguish objects that are no larger than an automobile.

The system consists of two wide-angle and four

narrow-angle television cameras, camera sequencer, a

video combiner, telemetry system, transmitters, and

Of the two wide-angle cameras (Fig, 16), one has a

l-inch lens with a speed of f / l and a field of 25 degrees.

The other camera has a 3-inch, f/2 lens with a field of

8.4 degrees. Of the four narrow-angle cameras (Fig. 17),

two have 3-inch, f/2 lenses with 2.1-degree fields of view,

while the others have l-inch, f/l enses with 6.3-degree

fields. Both wide- and narrow-angle cameras have a fixed

focus, but are able to take pictures from approximately

1120 miles to about ?hmile from the Moon’s surface.

All cameras have high-quality lenses with five ele-

ments and metallic focal plane or slit type shutters. This

shutter is not cocked as in conventional cameras, butmoves from one side of the lens to the other each time

a picture is taken. Shutter speed of the wide-angle cam-

eras is Woo second, and for the narrow-angle, Moo second.

One reason for having several cameras with different

lens apertures is that the lighting conditions on the

Moon can not be determined from Earth. The different

lenses provide greater exposure latitude. They are set

to take pictures from about 30 to 2500 foot-lamberts. This

corresponds roughly to lighting conditions on Earth (on

an average day) from high noon to about dusk.

Behind each of the cameras is a vidicon tube 1 inch

in diameter and 4.5 inches long. The inside of the face

plate of the tubes is coated with a photoconductive

material that acts in much the same way as tubes in

commercial television cameras. When a picture is taken,

the light and dark areas form on the face plate an image

of what the lens gathered as the shutter was snapped.

This image is rapidly scanned by a beam of electrons.

The beam is capable of differentiating light and dark

areas by their electrical resistance (high resistance, a

light area; low resistance, a dark area).

The image projected on the face plate of the wide-

angle cameras is 0.44 inch square, while the narrow-angle

camera vidicon face plates use only an 0.11 inch square.

The wide-angle camera pictures are scanned 800 times

by the electron beam but, because they occupy a smaller

area, the narrow-angle cameras are scanned only 200

times.

The scan lines, each containing information about some

part of the picture, are converted into an electrical signal.

They are sent through the camera amplifier where they

are amplified 1000 times.

Once amplified, the signal is sent to one of two video

combiners in the TV subsystem. There is one video com-

biner each for the wide- and narrow-angle cameras. They

combine sequentially the output of the cameras to which

they are mated. The output of the video combiners is

then converted to a frequency-modulated signal and sent

to one of the two 60-watt transmitters. One transmitter

sends pictures to Earth from the wide-angle cameras on

959.52 megacycles; the narrow-angle pictures are sent on

960.58 megacycles.

19

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Figure 16. Wide-angle camera of TV system Figure 17. Narrow-angle camera of TV system

The TV system also includes two batteries, one for

each channel. Each battery weighs 43 pounds. They are

made of 22 sealed silver zinc oxide cells and provide

about 33 volts. During the 14-minute operation, the hours.

wide-angle channel will use about 4.0 ampere-hours of

power while the narrow-angle channel will use 4.1

ampere-hours. The total power capacity is 40 ampere-

20

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The requirement is tw o-w ay communicat ions from launch to impact. The data han-

d l i n g sy s te m i s g e a re d to p ro v id e o p e ra ti on a l i n fo r m a t i o n a s n e e d e d , so t h a t

eng ineers w i l l be in cons tan t command o f the s i tuat ion.

Space Flight Operations

Planning and executing the inflight operations of themission are the primary functions of the Space Flight

Operations System (SFO). The SFO Director conducts

and directs the operation from the Space Flight Opera-

tions Facility (SFOF), located at JPL, Pasadena.

The space flight operations associated with the Ranger

Project will be the first to be conducted in the SFOF.

This is a new space age facility incorporating advanced

state-of-the-art electronic and mechanical equipments

used to conduct the mission. The SFO Director and the

supporting personnel have immediate and continuous

access to all mission information through the world-wideCommunications System which is part of the SFOF.

The SFO Director is supported by three groups com-

prising engineers and scientists who are specialists in the

areas of the spacecraft, its trajectory, and the scientific

experiments of the missions (Fig. 18).All events that are

pIanned to take place during the mission are tabulated in

their chronological order of occurrence. This schedule,

called the Standard Sequence of Events, is the summar-

ized plan by which the flight operations are conducted.

The SFO Director coordinates the supporting activitiesof the world-wide facilities that perform the tracking and

data recovery function. These facilities are the U. S. Air

Force Eastern Test Range (ETR) Tracking Network and

the NASA Deep Space Network (DSN).

The ETR Tracking Network covers the phase of the

mission from launch through Agena separation and pro-

vides the tracking data from which the initial orbit of the

spacecraft is computed. The ETR Tracking Network data

are sent to the SFOF over the commercial teletype and

high-speed data line. ETR also converts these data into

the look-angle information which is forwarded by theDSN to the Deep Space Instrumentation Facility (DSIF)

Stations to enable them to point their antennas for acqui-

sition of the spacecraft signals before the spacecraft

comes into their scope of view.

Operated by JPL for NASA, the Deep Space Network

is composed of the Deep Space Instrumentation Facility

and the Space Flight Operations Facility-a world-wide

system which functions to provide contact with the space-

craft during all phases of its flight.

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IIIIIIIIIIII

IIIII

I

I

IIIIIIIIIIII

22

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The eyes and ears of the mission are t--e DSIF Stations

a world-wide network of four permanent

2) : Echo and Pioneer, located at Gold-

South Africa. In addition, a mobile tracking station,

of the permanent sta-

with an 85-foot-diameter, parabolic-

t signals from thousands of miles out in space, over

6000 square feet of surface, and concentrates them

e pickup point of th e antenna dish. This

22,000 times. The Echo Station at Goldstone, and

is

as command capability-the capability to send

to the spacecraft at the direction of the Space

be utilized for sending the spacecraft commands

Characteristic

Antenna sire

Maximum angular

rate

Antenna gain

(960 Mc)

Tracking feed

Horn feed

Transmitter

power

Data transmission

Angles-doppler

Telemetry

Decommutated

telemetry

Command capability

Spacecraft

Monitoring

Station

6-foot (Az-El)

(no angle data)

Manually

operated

-

20.5 decibels

-Real time'

No

No

~~ ~~~~

tific, and TV pictures) transmitted from the spacecra

during the terminal phase of the mission. Additionally,

this station has a 50-watt transmitter for backup com-

mand capabilities. The Pioneer Station at Goldstone will

provide redundant receiving and magnetic tape recording

of the video data.

In addition to these stations, the prelaunch checkout of

the spacecraft and reception of telemetry data (until loss

of sight) is accomplished by a DSIF checkout facility at

Cape Kennedy.

The four permanent stations are located around the

Earth's equator in such a way that communications with

the spacecraft can be constantly maintained.

Through the DSIF, two-way communication with the

spacecraft is maintained, information of its position ob-

tained, engineering and scientific telemetry received, and

commands to the spacecraft sent.

Table 2. Capabilities and characteristics

Mobile

Tracking

Station

10-foot

(AI-El)

20 degrees per

second in

both axes

23.5 k0.2

decibels

-

25 watts

Near-real time

None

No

No

Goldstone

Pioneer

Station

65-foot Polar

(HA-Dec)

0.7 degree per

second in

both axes

-

45.7 f0.6

decibels

-

Near-real time'

Record only

No

No

Goldstone

Echo

Station

65-foot (Polar

(HA-Dec)

0.7 degree per

second in

bath axes

-

45.7 f 0.8

decibels

200 watts ( 5 0 -

watt backup)

Near-real time'

Near-real-time

Reo1 timeo

Ye s

Ye s

Woommra

Station,

Australia

65-foot Polar

(HA-Dec)

0.7 degree per

second in

both axes

43.7 k0.9

decibels

-

200 watts

Near-real time

Near-real-time

Real time'

Yes

Yes

Johannesburg

Station,

South Africa

65-foot Polar

(HA-Dec)

0.7 degree per

second in

both axes

43.7 f0.9

decibels

-

200 watts

Near-real time

Near-real-time

Real time'

Yes

Ye s~~ ~~~~ ~~~~

'Sent to the Telemetry Processing Station (TPS) v ia w id e -b o n d te le p h o n e l in e .' A n g l e dola not the result of autotrack operation.

23

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Figure 19. Space Flight Operations Facility

All data obtained by the DSIF during the mission are

transmitted to the Space Flight Operations Facility at

JPL, Pasadena (Fig. 19), by way of the commercial tele-

type, high-speed data lines, wide-band and voice tele-

phone circuits, and a microwave net. These data are

relayed to the Data Processing System (DPS) (Fig. 20),

of the SFOF.

The DPS is used to generate the spacecraft orbit fromthe tracking data received, pointing and prediction infor-

mation for the tracking antennas of the DSIF and for the

reduction of engineering telemetry data which is proc-

essed in near-real-time and relayed to the flight oper-

ations personnel. The commands for spacecraft midcourse

and terminal maneuvers are generated through the use

of the DPS.

Pertinent data are relayed throughout the SFOF by

the Data Display System of the SFOF, making it imme-

diately available to the people who are actively involved

in the mission: the Ranger Project Manager, who co-

the Space Flight operations Director informed

of, the status and performance of the spacecraft in

flight in accordance with established procedures.

This group recommends the use of real-time com-

mands to improve the performance of the spacecraft

in the event of a nonstandard mode of operation,

and to provide such spacecraft performance infor-

mation as may be required by other operational

areas to perform their assigned tasks and functions.

( 2 )Flight Path Analysis and Command. It is the respon-

sibility of this group to evaluate and use the track-

ing data (as well as the Spacecraft Data Analysis

Team’s evaluation of pertinent telemetry data) in

order to determine the actual trajectory and atti-

tude of the spacecraft during flight. From such

data, this group supplies the tracking stations with

acquisition and prediction information, and supplies

the Space Flight Operations Director with the

necessary command information for the midcourse

and terminal maneuvers (if required).

( 3 )Space Science Analysis and Command. It is the

responsibility of this group to control the flow of

data related to the scientific experiment during the

interval between its receipt from the tracking sta-

tion and its transmission to the appropriate scien-

ordinates and directs the mission-activities (Fig. 21); the

engineers who command, monitor, and control the behav-

ior and performance of the spacecraft; and the Space

Scientists who acquire, analyze, and evaluate the data

gathered from the mission (Fig. 22).

tists. This group supplies recommendations as to

the effect of various maneuver possibilities on the

scientific experiment. Any analysis or inflight eval-

The specialized technical groups that provide support

to the decision making process are:

(1)The Spacecraft Data Analysis Team. It is the re-

sponsibility of this group to determine, and to keep

uation of the scientific da ta will be supplied by

this group.

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c

Figure 20. Data Processing System

The functions of the SFO system, supported by the

DSN could be summarized as follows:

(1 )Monitor the spacecraft’s departure from Earth.

(2) Record its path.

(3 ) Plot its trajectory.

(4) Collect and transcribe its coded commentary.

( 5 )Decode these reports into information about what

(6 ) Calculate the flight path changes necessary to reach

(7 ) Forward the corrective commands.

(8 )Analyze and convert its mission-acquired informa-

it is doing, seeing, and experiencing.

its destination.

tion into knowledge for the benefit of man.

Figure 22 . Operations Area

Figure 21. Mission Control Rooms

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AERODYNA

RANGER

, M I C SHROUD

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Simi la r to the famous M ar iner , the Ranger spacecra f t i s des igned to opera te re -

l iab ly in the env i ronment o f space . The miss ion is s imp le : Go out f rom Ear th , de l iv e r

cameras over the lunar sur face, and receive th eir p ic ture s b ack o n Ear th.

Mission Description

Night Through lnjection

The launch vehicle, Atlas D, will boost the Ranger

spacecraft to an altitude of 115 statute miles. During this

launch phase, the Ranger spacecraft is protected against

aerodynamic heating by a shroud which is jettisoned by

spring-loaded bolts just prior to separation of the Atlas

from the Agena (approximately 5 minutes after liftoff).

As shown in Fig. 23 , the Atlas booster separates from the

Agena and the Agena pitches down from an altitude of

nearly 15degrees above, to almost level with, the Earth‘s

horizon. Its engine fires and burns for approximately

2?/2 minutes to accelerate it and the spacecraft to an

orbital speed of 17,500 miles per hour.

The Agena and Ranger then coast in the parking orbit

over the Atlantic Ocean. When they reach a preselected

point, the Agenu engine fires for a second time. At the

conclusion of this second burn, the Agenn and spacecraft

are injected into a lunar flight path at a velocity sufficient

for their escape from Earth. The second firing accelerates

the spacecraft to approximately 24,500 miles per hour.

The injection point and the Moon trajectory are illus-

trated in Figs. 23 an d 24 . Following injection, spring-

loaded explosive bolts are fired to separate the Agena

from the spacecraft. Fig. 25 shows the Agena as it per-

forms a 180-degree turn and a retro maneuver to remove

it from the spacecraft trajectory. Propulsion for the retro

maneuver is provided by a small, solid-fuel rocket motor.

This maneuver ensures that the Agenu will not impact

the Moon and that it will not be in a position to reflect

light that could confuse the Ranger’s optical sensors and

cause them to mistake the Agena for the Earth.

The spacecraft’s separation from the Agena automat-

ically starts the Ranger’s mechanical back-up timer arid

TV back-up clock and releases the CC&S for issuance of

flight commands. Prior to this point, the CC&S is par-

tially inhibited to ensure that flight commands will not

be given inadvertently during the launch phase.

The CC&S gives its first command, 23 minutes after

launch, ordering the Ranger transmitter to full 3-watt

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Figure 24. Ranger nominal trajectory to Moon

of the spacecraft is accomplished by the attitude control

system’s combining of signals received from its Sun

sensors and the autopilot’s rate gyros.

At the same time that the CC&Sorders Sun acquisition,it orders the high-gain directional antenna extended. A

drive motor extends the antenna to a present hinge

angle that was determined before launch.

In order to conserve gas, the attitude control system

permits a pointing error of ?hdegree on either side of the

Sun making the total pointing error 1 degree. If the

error becomes greater, the sensors signal the gas jets and

they fire as necessary to again lock the spacecraft onto

the Sun. It is calculated that on the average the gas jets

fire for Y,oof a second every 60 minutes to keep the space-

craft’s solar panels pointed at the Sun.

The Sun acquisition process is expected to take about

30 minutes. As soon as the solar panels are locked on theSun, the power system begins drawing electric power

from the panels. After that time, the batteries only supply

power in the event of a peak demand that the panels

cannot handle and during the midcourse and terminal

maneuvers.

h r t h Acquisition

The next sequence of events commanded by the CC&S

is the acquisition of Earth by the high-gain directional

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AGENA YA W

Figure 25 . Agena-Ranger separation sequence

antenna. This action is initiated at approximately 3%

hours after launch. A capability is provided to back up

the initiation of this event by a radio command from

Earth, if necessary. The attitude control system’s Earth

sensor is activated (its secondary Sun sensors turned off),

and discharges from the gas jets roll the spacecraft.

The spacecraft maintains its lock on the Sun and, with

its high-gain directional antenna pointed at a preset

angle, rolls about its long axis and starts looking for the

Earth. I t does this by means of the three-section, photo-

multiplier tube operated Earth sensor mounted on, and

aligned with, the high-gain antenna. During the roll,

the Earth sensor sees the Earth and informs the attitude

control system. Gas is discharged from the jets as re-

quired to keep the Earth in view of the sensor, and thus

30

lock onto the Earth. Earth acquisition requires approxi-

mately M hour.

With the completion of Earth acquisition (Fig. 13),

the spacecraft is stabilized on three axes-the pitch and

yaw which keep the spacecraft solar panels pointed

at the Sun, and the roll axis which keeps the direc-tional antenna pointed toward the Earth. There is some

danger that the Earth sensor, during its search for the

Earth, may see and lock onto the Moon. But telemetry

later will inform Earth stations if this has occurred, and

Earth stations have the ability to send an override com-

mand to the attitude control system to tell it to look

again for the Earth. If such action is not sufficient, the

stations can send a hinge override command to change

the hinge angle of the high-gain antenna and then order

8/7/2019 Ranger 1964-65


nother roll search. When the Earth is acquired, the space-

s transmitter is switched from the omni-antenna to

-4 ise in signal strength on Earth will be an indication

hat acquisition of the high-gain antenna has been

chieved. Confirmation will be afforded by analysis of

telemetry to determine the angle of the antenna hinge.

With Sun and Earth acquisition achieved, Ranger is in

its cruise mode.

Cruise und Midcourse Phuse

Ranger continues in cruise mode until time for the

midcourse trajectory correction maneuver (Fig. 26). After

launch, most of th e activity on the lunar mission is

centered at the DSIF Stations and at the Space Flight

Operations Facility at JPL.

Tracking data collected by the stations are sent to JPL

and fed into a large-scale computer system. The com-

puter compares the actual trajectory of Ranger with the

course required to yield a collision course with the Moon.

If a correction is necessary to achieve the proper flight

path, the computer provides the necessary figures to

command the spacecraft to alter its trajectory. This in-

volves determining the proper roll and pitch commands

to point the spacecraft for the trajectory correction. Then

the appropriately timed motor burn will provide the

velocity required to change the direction and velocity

of the flight.

The order of events is precise. The first command from

Goldstone to the spacecraft gives the direction and

amount of roll required; the second gives the direction and

amount of pitch needed; the third gives the velocity

change determining the motor burn time. These data are

stored in the spacecraft CC&S until Goldstone transmits

a go command.

Prior to the go command, Goldstone will have ordered

the Ranger transmitter to switch from the high-gain

directional antenna to the omnidirectional antennamounted at the peak of the superstructure.

Commands preprogrammed in the CC&S for the mid-

course sequence initiate the following: The Earth sensor,

mounted on the high-gain antenna, is turned off and the

antenna itself moved out of the path of the midcourse

motor’s exhaust; the autopilot and accelerometer are

powered; and pitch and roll turns are initiated. During

the maneuver, the CC&S will inform the attitude control

subsystem of the pitch and roll turns, as they occur, for

reference against the orders from Earth. An accelerom-

eter will provide acceleration rates to the CC&S during

motor burn. Each pulse from the accelerometer repre-

sents a velocity increment of 0.03 meter per second.

The roll maneuver requires a maximum of 9%minutes

of time, including 2 minutes of settling time; the pitch

maneuver requires a maximum of 17 minutes, including2 minutes of settling time. When these are completed,

the midcourse motor is fired and burns for the required

time. Because the attitude control gas jets are not power-

ful enough to maintain the stability of the spacecraft

during the propulsion phase of the midcourse maneuver,

movable jet vanes extending into the exhaust control the

att itude of the spacecraft in this period.

The jet vanes are controlled by an autopilot in the

attitude control subsystem that functions only during

the midcourse maneuver. The autopilot accepts informa-

tion from the gyros to direct the thrust of the motorthrough the spacecraft’s center of gravity in order to

stabilize the craft.

After the midcourse maneuver has placed the Ranger

on the desired trajectory, the spacecraft again locks onto

the Sun and Earth, transmissions are switched from the

omni-antenna back to the high-gain directional antenna,

and thus the spacecraft is again in the cruise mode.

Terminul Phuse

Approximately 67 hours after launch (exact time de-pending on day and hour of launch), the Goldstone

Station prepares to radio commands to the Ranger to

instruct the spacecraft to perform the terminal maneuver

(Fig. 27 ) , if required. This maneuver positions the space-

craft in the proper attitude, and thus aligns the six

cameras with the descent path of the spacecraft as it

drops to the Moon’s surface.

JPL computers are determining the position of the

spacecraft in its cruise mode in relation to the desired

position for the terminal phase and are furnishing the

angles and duration of the terminal commands. These

are encoded, transmitted to the spacecraft, and stored in

the CC&S.A radio command will have already been sent

to prevent the television timer from causing early turn-on

of the television system.

The first pitch command is followed by a command

that yaws the spacecraft and then by a second pitch

command. Completion of the terminal maneuver will

require about 34 minutes. In the terminal mode, the

spacecraft’s solar panels are turned partly away from the

Sun.

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Figure 26. Ranger midcourse maneuver sequence

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TV Sequence

At 1 hour before lunar impact, the DSIF Goldstone

Tracking Station sends instructions to Ranger to begin

the terminal maneuver which will point the cameras in

the direction the spacecraft is :rave!ing.

lunar

altitude,

miles

First pictures 1 1 2 0

Last pictures 4

Y3

At impact minus about 15 minutes, the CC&S sends a

command to turn on the television system for warmup.A redundant command is provided by the Goldstone

Station. At this point, the spacecraft is approximately

1180 miles from the Moon; its velocity has accelerated to

approximately 4400 miles per hour because of the increas-

ing effect of the lunar gravity.

Cameras

Full view, Partia l view,

square miles square miles

1-inch 3-inch 1-inc h 3-inch

lens lens lens lens

180,000 19,000 12,500 1200

- -Y2 YZ

- - 11770 1.17000

At impact minus approximately 14 minutes, the camera

sequencers send a command to turn the cameras on full

power. This command will be backed up by another from

the CC&S at impact minus 10 minutes.

From the time that the cameras start taking pictures

until Ranger crashes on the Moon’s surface, the two wide-

angle cameras will take one picture every 2.56 seconds

or about 160 pictures each. The spacecraft is falling at a

velocity of 4450 miles per hour. Each of the narrow-angle

cameras takes 976 pictures during the descent phase, 01

one picture every 0.2 second.

As indicated in Table 3, the first picture taken by the

wide-angle camera equipped with the 1-inch lens shows

a surface area of about 180,000 square miles. The last

picture taken by the narrow-angle camera with 3-inch

lens will include an area of about M square mile.

It is impossible to tell beforehand which camera will

take the last picture. Because of this, the unknown light-

ing conditions, and the possibility that the angle of

impact might not be vertical, the resolving power of the

cameras cannot be exactly predicted.

The pictures transmitted to Earth are received b y two

85-foot-diameter parabolic antennas at the Goldstone

Tracking Station (Figs. 28 and 29). These stations have

special equipment to record the pictures on %-millimeter

film and also on magnetic tape.

Because the video data are transmitted by radio, a

certain amount of noise will be present on the signals that

form the pictures. This noise will be removed through

superposition techniques; stereo evaluation will be per-

formed wherever possible. The films will be analyzed by

a staff of scientific investigators and experimenters.

Table 3. lunar area covered by TV cameras (typical)

Figure 27. Ranger terminal maneuver sequence

33

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Figure 28. Echo Station

Figure 29. Pioneer Station

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Documents

Ranger 1964-65